Sector Performance: IYJ tracks US aerospace and defense companies. If this sector performs well due to increased defense spending or positive industry news, IYJ's price tends to rise.

Company Performance: The performance of major holdings in IYJ, such as Boeing and Lockheed Martin, significantly impacts its price. Positive earnings reports or contract wins for these companies usually boost IYJ.

Economic Conditions: Overall economic health can influence the aerospace and defense sector. Strong economic growth can lead to increased air travel and demand for aircraft, potentially benefiting IYJ.

Geopolitical Events: Global conflicts or increased geopolitical tensions often drive defense spending, positively affecting IYJ's price. Conversely, peace initiatives may negatively impact it.

Interest Rates: Changes in interest rates can affect the cost of borrowing for aerospace and defense companies, impacting their profitability and consequently, IYJ's price.

Government Regulations: Changes in government regulations regarding defense contracts or export policies can impact the revenue and profitability of companies within IYJ.

Investor Sentiment: General market sentiment towards the aerospace and defense sector can influence demand for IYJ, affecting its price regardless of fundamental factors.

Supply and Demand: Basic economics of supply and demand also apply. If there is high demand for IYJ shares and limited supply, the price will increase and vice versa.